and even served as a source of reinforcements. So when the Bulgarian advance against the Serbians stalled, General Dimitriev was ordered to dispatch the 3/5 Infantry Brigade (45th and 46th Infantry regiments) to reinforce the 5th Army. In exchange, he was promised the 1st Army's 2/5 Infantry Brigade. On 20 June, General Mihail Savov was replaced by General Dimitriev as deputy commander-in-chief and the 3rd Army was placed under the command of General Racho Petrov. By that time, the Bulgarian command finally decided to utilize the inactive 1st and 3rd Armies and gave them orders to take the Serbian town of Knjaževac and then with their combined force to seize the fortress of Pirot. The force facing the Bulgarian 3rd Army was the Serbian 2nd Army – a total of around 35 battalions, 13 batteries and three squadrons, many of whom were third-line troops. The Serbian defense was centered around the important road and railway junction of Pirot. The Bulgarian 3rd Army was ordered to attack and pin down as many Serbian troops as possible while the 1st Army completed its primary objective in the north and then turned south to encircle Pirot. In order to achieve this task, General Petrov, following the orders of General Dimitriev, divided his forces into two groups. The Right Group that consisted of the 13th Infantry Division and 1/1 Infantry Brigade was to attack Pirot while the Left Group (also known as Tran Detachment), that was formed by the 2/1 Infantry Brigade, 2/5 Infantry Brigade, the Cavalry Division and the 46th Regiment, was to advance in the direction of Vranje. Due to the distance between the two groups, the forces operated independently. The only link between them was a single battalion supported by a cavalry squadron and two batteries. The Left Group advanced first on 22 June. The bad weather, poor roads and fog hampered the speed of movement of the units and the strong Serbian positions prevented any important Bulgarian gains. On 5 July, the Group deployed around Tran with its 18 battalions, 2 squadrons and 11 batteries and was placed under the commander of the 5th Danube Division. The army headquarters ordered it to attack, penetrate the Serbian defensive line and cut the communication lines between Vranje and Niš. After several days of fighting, on 12 July the Bulgarians managed to dislodge the Serbians from their main defensive line at Bukova Glava